1. Technical Field
Exemplary embodiments of the present disclosure generally relate to a fixing member, a fixing device, and an image forming apparatus.
2. Related Art
In recent years, electrophotographic image forming apparatuses such as copiers and printers have been directed toward full-color image formation, and the ratio thereof has been gradually increasing. Typically, a color electrophotographic image forming apparatus includes an image forming unit that forms a color image formed of toner images of four colors (cyan, magenta, yellow and black) on a recording medium, and a fixing device that fixes the formed toner images on the recording medium. The fixing device includes a heater for heating the toner images on the recording medium, a fixing member for fixing the toner images onto the recording medium, and a pressing member forming a fixing nip between the pressing member and the fixing member. The toner images are fixed onto the recording medium by heating and pressing the toner images when the recording medium passes through the fixing nip.
The fixing member having a belt shape or a roller shape is known. The fixing member includes those formed by providing an elastic layer made of a heat-resistant rubber on a base member such as a metal roller or a resin seamless belt, and those formed by further providing a release layer on the elastic layer. Generally, a member formed by integrating the heater inside the roller (heat fixing roller) is used as the fixing member having the roller shape. Further, the fixing member having the belt shape providing the heater inside the belt wound around rollers is also well known.
The fixing member needs to flexibly adhere to the toner images and efficiently conduct heat so that toner images (usually toner images of four colors) of multiple colors constituting full color are evenly heated. Thus, silicone rubber having flexibility and heat resistance is often used for the fixing member. However, silicone rubber has low thermal conductivity and thermal conduction to the toner image may become slower.
When thermal conduction to the toner image is slow, a lot of time is required to heat a surface of the fixing member to a fixing temperature for fixing the toner images. In a case of a high-speed machine, supplying of heat may be too slow. In addition, warm-up speed of the image forming apparatus may become slow. It is important to note that the warm-up speed with respect to temperature increase of the fixing member of the fixing device often limits the rate of warm-up speed of the image forming apparatus, as a whole, when powered on.
As a method to resolve the above-described problems, a technique for shortening the warm-up time of an imaging device is disclosed in JP-2008-191557-A, JP-2008-197585-A and JP-2009-092826-A. In the technique, thermal conductivity of the elastic layer is enhanced by blending carbon fibers in silicone rubber, and thermal capacity of the elastic layer is reduced by providing hole portions in silicone rubber. The above-described technique is effective for thermal diffusion. However, a problem of deformation (compressed permanent deformation) that does not easily recover may occur when the elastic layer having a configuration of silicone rubber including the carbon fibers and the hole portions is subjected to pressure over a long period under a stationary condition. When compressed permanent deformation occurs to the fixing member, the fixing member cannot evenly heat the toner images, and uneven gloss of an image or defective image fixing may occur.
As a method to resolve the above-described problem, a method of blending polyhydric alcohol in silicone rubber to enhance resistance to compressed permanent deformation is disclosed in JP-2011-227512-A and JP-4697493-B. However, compatibility of polyhydric alcohol and silicone rubber is poor. En a case of blending polyhydric alcohol to silicone rubber, viscosity increased and restriction to manufacturing conditions occurred as a result. In addition, the above-described method is insufficient to resolve uneven gloss of an image. When silicone rubber having polyhydric alcohol is left under pressure over a long period, compressed permanent deformation occurs to silicone rubber having polyhydric alcohol and uneven gloss of an image occurs.
JP-2006-154711-A describes a fixing member for toner images having a solid material dispersed in a silicone layer instead of a conventional silicone rubber layer provided with hole portions that is a cause for susceptibility to deformation. JP-2006-154711-A also describes lowering viscosity of a silicone resin by adding an organic solvent and blending the solid material when forming the fixing member for toner images. The solid material described in JP-2006-154711-A reduces the amount of heat release of the fixing member and suppresses power consumption, and has low thermal conductivity and good thermal insulation. A typical example is silicone beads. In addition, JP-2006-15471 I-A describes that the organic solvent preferably has a relatively low boiling point such as C1-C4 alcohol, C3-C12 hydrocarbon, benzene, toluene, xylene, tetrahydrofuran, acetonitrile, dimethylformamide, or dimethylsulfoxide.